1. Field of the Invention
The present invention relates to the field of communications. More specifically, it relates to a method through which any standard private branch exchange (PBX) is able to be interfaced with a wireless communications network and also with the public switched telephone network (PSTN).
2. Description of the Related Art
Today's business customers demand cost effective communications systems that satisfy a wide range of applications. These applications include basic and advanced voice call coverage and handling, station user mobility, call center solutions, telecommuting, data network connectivity, messaging, etc. Ease of operation and administration is always an important factor in selecting a communication system, as is the possibility of future expansion. To fulfill these and other needs, many businesses have employed private branch exchanges (PBXs).
Private branch exchanges are commonly employed in today's business communications systems for locally providing many of the above-identified features and services within an organization using telephone services while simultaneously acting as an analog or digital switchboard for connecting private telephone networks to the PSTN. For example, PBXs are typically utilized by groups of subscribers located in one geographic area, such as employees of a company located within a common building. The PBX services as few or as many users as the application requires.
Many different types of PBXs currently exist in the marketplace to provide such services. A problem that currently exists in the field of wireless communications, however, is the fact that standard PBXs, such as e.g., the Lucent Technologies, Inc. DEFINITY® system, are not compatible with the interface equipment (e.g., audio switches, etc.) used in many wireless networks. Moreover, the interface equipment (e.g., audio switches, etc.) are not compatible with the PSTN in that they do not necessarily implement all the protocols necessary to effectively communicate with the PSTN and, thereby connect the wireless system to the PSTN. Therefore, customers in need of wireless telephone services have been forced to specify and build expensive custom PBXs to interface with their wireless communications networks and the PSTN.
Turning to FIG. 1, a typical wireless communication system is depicted in which a wireless communications network 130 communicates with a custom PBX 115 which in turn communicates with a central office (CO); part of the PSTN 120. Within thc wireless communications network 130, a plurality of wireless communication devices (e.g., radio transceivers) 100 wirelessly communicate with a two-way radio console 105 via a controller 125, which controls communication resource allocation (e.g., access to wireless links). An audio switch 110 is used to route audio throughout the wireless communication network 130 dependent upon instructions received from wireless communication network controller 125, as is known in the art. Typically, a custom designed PBX 115 is required to interface with the audio switch 110 and the PSTN 120 since currently, there does not exist a standard “off the shelf” PBX that is able to communicate with both a wireless communications network and the PSTN. The custom designed PBX 115 provides system users (i.e., those placing calls from a mobile transceiver unit 100 to a central office and vice versa) with many desirable features (such as e.g., those described above), and also serves as an interface between the wireless network 130 and the PSTN 120 for providing necessary signaling protocols to both the wireless network 130 and the PSTN 120, thereby enabling communication between individual transceivers 100 of the wireless communication network 130 and the central office.
While custom PBXs have performed satisfactorily for this application, they remain a very expensive alternative to standard “off the shelf” PBXs. Furthermore, customers relying upon these custom PBXs must also forego the tested quality, reputation, technical support system, scalability and reliability of a standard “off the shelf” PBX. In addition, forward compatibility (e.g., when new features are introduced) and maintenance support become very expensive with custom PBXs. Thus, a system and method for using a standard PBX to interface with both a wireless communications network and the PSTN is desirable.